Radiant heat sensitive device



Fb.27, 1940. I R.VA.BEVERIDGE 2,191,640

RADIANT HEAT SENSITIVE DEVICE Filed Dec. 22, 1937 S l Bnnentor Patented Feb. 27, 1940 j UNITED STATES PATENT OFFICE suffix: 21:53.? time...

to Minneapolis-Honeywell Regulator Company,

. eapolis, Minn, a corporation of Delaware Application 22, 1937, Serial No. 181,122-

8 Claims.

This invention relates generally to a heat sensitive switch, and more particularly to that type ofswitch which responds to the radiant heat of combustion, and opens and closes depending upon whether or not there is combustion within the furnace.

In devices of this character it is customary to provide a tube which is inserted through the furnace wall and positioned to look directly at the fire. A heat responsive device is located at the end of the tube outside of the iumace and this heat responsive device will be subjected to considerable radiant heat from the fire, but as it is situated well back in the tube it will get -very little heat by conduction or convection. As combustion takes place the radiant heat from the fire is absorbed by the heat responsive device which responds and actuates a switch through the medium of a slip friction connection. when 2 the fire is extinguished the heat radiated to the heat sensitive device will be greatly decreased and the heat already absorbed by it will be dissipated outwardly through its casing causing it to again respond and immediately actuate its switch 25 due to the slip friction connection.

It is an object of this invention to provide a means for rendering devices of the above char-'- acter more sensitive to the starting up and shutting down of a fire within a furnace.

30 Another object of the invention is to provide a damper between the heat sensitive device and the fire which is opened when the fire producing means is energized so that if combustion occurs the radiant heat from the fire can heat 35 the heat sensitive device, and is closed when the fire producing means is deenergized so that.

radiant heat from the walls of the furnace cannot reach the heat sensitive device and retard its cooling.

40 In the case where a fire has burned fora while and the furnace and stack have become heated, there is a natural draft through the furnace and up the stack. If now the fire is extinguished there will be a temporary reduction .45 in pressure within the combustion chamberrbelow atmospheric pressure. Advantage is taken of this fact in the present invention by taking a device of th e'character described aboveand cutting holes in the casing by the heat sensi- 50 tive device so that when the fire is extinguished and the lowered pressure occurs in' the com-.

bustion space, room air will be sucked into the casing, over the heatsensitive device, into the furnace and up the stack. This passage of room 55 air over the heat sensitive device helps to carry away its heat after the fire is extinguished and therefore makes the device more sensitive. The damper, referred to above, is a loose fit in the tube so that the air has plenty of opportunity to be drawn through the tube, and into the fur- 5 nace.

These and other objects will become apparent as the following specification is read with reference to the accompanying drawing, in which Figure 1 is a view showing the manner in .10 which the device of this invention is mounted in the wall of a furnace;

Figure 2 is a side view of the invention, partly in elevation and partly in a section taken along the line 22 of Figure 1; 15

Figure 3 is an end view looking into the tube at. the damper and heat sensitive diaphragm; and

Figure 4 is a diagram of an oil burner control circuit in which the present invention may be used.

Referring firstvto Figure 2, a tube II is provided with an annular flange I2 against which is placed annular heat insulator l3 and an annular gasket. Against the gasket is placed a thin metal disc 15 which is blackened on one side so that its absorption of radiant heat will v be accelerated. A casing I6 is provided with an annular flange I! which abuts the disc l5 and through bolts ll-a're provided for integrally connecting the casing 'and the tube along with the other members recited. The casing I6 is provided with a partition is having a hole 20 therein through which passes a ribbon 2|, one end of which is connected to the center of the diaphragm I! by a suitable connecting means 22. Bracket 23 is fastened to the partition I9 by a suitable means, not shown, and this bracket is provided with a pair of ears 24 between which a wheel 25 rotateson an axis 28. The bracket 13 is provided with a second ear 21 to which i is connected a spring 23. The ribbon 2| engages the surface of the wheel 2! for a portion of its circumference and is connected to one end of the spring 28 by some suitable connecting means 4.5 29. The center portion 3| of the spring 28 is wound several times about a member 30 and exerts an upward pull on the ribbon 2| as viewed in Figure 2. Moimted on the axis 26 and rigidly connected with the wheel 25 is an arm 3| to the free end of which is connected as at 32 a flexible contact carrying member 33. A partition 34 of insulating material is held adjacent to a shoulder 35 of casing it by means of screws 36. The flexible arm 33 which carries contacts 31 and 38 extends through hole 39 in the partition 34. Mounted immediately above the hole 39 by means of screw 43 is a. bracket 4i carrying stationary contact 42, and located immediately below the hole 39 and fastened to partition 34 by means of screw 43 is a bracket 44 carrying the stationary contact 45. Conductor 46 is connected to bracket 4! by means of screw and conductor 41 is connected to the bracket 44 by means of screw 43. Conductor 48 is connected to a screw 49 extending through the insulating partition 34 and conductor 50 is connected to the screw 49 on the other side of the partition 34 by means of nut 5| and in turn is connected through the connecting means 32 to the flexible contact arm 33. A nipple 52 is provided at the lower part of the casing l6 through which the conductors 46, 41 and 48 extend. A cap 53 closes the open end of the casing l6 and is fastened thereto by means of screws 54.

The device so far described is old and forms no part of the present invention. It is intended to be applied to a furnace so that it may respond to the radiant heat of the fire. The manner of mounting this instrument is shown in Figure 1, wherein the tube l I is shown mounted in the wall 55 of a furnace and directed so that the open end of the tube looks directly at the flame 56 produced by the oil burner 51.

When there is no fire in the furnace and the device is in its cold position, the diaphragm I5 will be more or less straight and the contacts 38 and 45 will be in engagement. When the oil burner is put into operation and combustion occurs the radiant heat from the fire will pass through the tube H and be absorbed by the blackened surface of the diaphragm l5 which will commence to heat up very rapidly. The central portion of the diaphragm which absorbs the radiant heat will become considerably hotter than its periphery, which will cause it to expand and buckle. A constant pull is exerted on the center of the diaphragm through the medium of the ribbon 2i and the spring 28 which will cause movement of the diaphragm to the left as viewed in Figure 2 when it expands. This movement will cause a consequent movement of the ribbon 2| which will rotate the roller 25 in a clockwise direction and carry with it arm 3| and the resilient contact carrying arm 33, which will cause disengagement of the contacts 38 and 45 and engagement of the contacts 31 and 42. Further movement of the arm 3| is prevented by the engagement of these contacts but any further movement of the diaphragm l5 will be taken care of by the ribbon 2| slipping over the surface of the wheel 25. As the fire continues to burn the diaphragm l5 will continue to absorb more and more heat, the central part of the diaphragm will remain hotter than the periphery due to the fact that the heat will be conducted along the diaphragm to the periphery and dissipated to the air in the room. This insures that the periphery of the diaphragm will always remain comparatively cold so that the diaphragm will remain buckled as long as a fire exists in the furnace.

When the fire becomes extinguished there will be a very great reduction in the amount of radiant heat which will strike the diaphragm l5 so that it will commence to cool rapidly. This cooling will cause it to straighten out and as it does so it will pull the ribbon 2| toward the right as viewed in Figure 2, thereby rotating the wheel 25 in a counterclockwise direction, which will carry with it arms 3! and 33. This will cause disengagement of the contacts 3'! and 42 and engagement of contacts 38 and 45. The device will then be in its cold position again. It is understood of course that any excess movement of diaphragm 15 to the right after the contacts 38 and 45 have been closed will be absorbed by the ribbon 2i slipping with respect to the wheel 25.

The present invention involves an addition to this structure for the purpose of rendering the diaphragm I5 more sensitive to combustion within the furnace and particularly more sensitive to the extinguishment of the fire. A bracket 58 is fastened to flange l2 by means of the screw 59. This bracket has a shelf 50 on which is mounted a casing 6! which uses a solenoid 52 having a winding 63. Mounted on a transverse shaft 64 extending diametrically through the tube H is a butterfly damper 65. The shaft 64 is pivotally connected by means of a crank arm 66 as at 61 to a link 58 which is in turn pivotally connected at 69 to a plunger 10 for the solenoid 62. Energization of the solenoid winding 63 causes a rotation of the crank 66 in a clockwise direction until it strikes the stop H which is fastened to the tube II, at which time the damper 65 will be in a horizontal position longitudinally of the tube H so that it will permit radiant heat to enter the tube II and strike the diaphragm I5. Bracket 58 is provided with 'an ear 12 having a small hole 13 through which one end of a coil spring "I4 is inserted. The other end of spring 14 is hooked imder the pin 61 which pivotally connects the arm 66 with the link 68. Thus when the winding 53 is deenergized the spring 14 will pull the crank arm 66 downwardly to rotate it in a counter-clockwise direction through an angle of 90 until it strikes the stop 15, at which time the damper 65 will extend transversely across the opening through the tube II. This will prevent radiant heat from passing through the tube and striking the diaphragm I5.

The reason for providing the damper 65 is that when the fire is extinguished in the furnace, although there can be no radiant heat from the flame which will pass to the diaphragm l5, yet there is a considerable amount of radiant heat which passes from the walls of the furnace to the diaphragm and such radiant heat has a material effect on the cooling down process 01' the diaphragm. With the addition of the damper 65 to this control device, it will be seen that where the winding 63 is wired in parallel with the burner motor that when the motor is deenergized the winding 53 will be deenerglzed, which will allow the spring 14 to rotate the damper 65 to the position where it extends across the tube ll so that any radiated heat from the walls of the furnace cannot strike the diaphragm l5 and delay its cooling action.

Where the burner has been operating and the furnace and stack has become heated up there is a natural draft through the furnace and up the stack due to the heating of the elements. If now the burner motor is dee'nergized or the fire becomes extinguished for some other reason the natural draft due to the heated stack will then lower the pressure in the combustion chamber to a value where it is lower than atmospheric. Advantage may be taken of this fact by boring holes such as shown at 14 through the annular heat insulator l3. These holes are placed at an angle so that the reduced pressure within the furnace will cause room air to pass through the holes directly onto the diaphragm I5 and thence out through the tube H and around the damper 85, which it will be noted from Figure 3 fits very loosely within the tube I I and into the furnace trol circuit in which this invention may be used,

to the secondary 83 of the transformer 88. A

to advantage will now be described. Supply conductors 11 and 18 feed the primary winding 19 of the transformer 88 through conductors 8I and 82. The secondary 83 of this transformer is connected by means of conductor 84 to one end of relay coil 85, the other end of which is connected by conductor 88 to a conductor 81 leading to one end of a heating element 88 for the safety switch 89. This safety switch is operated by means of a bimetallic element 98 and is of the type which breaks the circuit after its heater has been energized for a predetermined time and then must be manually reset. This safety switch forms no part of the present invention and may be of the type disclosed in the Denison Patent No. 1,958,081. The other end of the heater 88 is connected by means of the. conductor 9I to the switch arm 33 of the combustion responsive switch. The cold contact of this switch is connected by means of conductor 92 to stationary contact 93. Stationary contact 94 which is engaged by the bi-- metallic element 98 is connected by conductor 95 room thermostat 98 is provided which comprises a bimetal' coil 91 to which is attached a flexible switch arm 98 and a rigid switch arm 99. Flexthemostat 98. Conductor ible switch arm 98 is adapted to engage stationary contact I88 which is connected by means of conductor I8I with bimetallic element 98. Relay coil is adapted to operate two switch arms I82 and I83. The switch arm I82 engages stationary contact I84 which is connected by means of conductor I85 with the bimetallic coil 91 of the room I88 connects the switch arm I 82 with the conductor 9|. A conductor I81 connects stationary contact I88 with the supply line 11. Switch arm I83 is adapted to cooperate with the contact I88 and this switch arm is connected by means of conductors I89, H8 and III to the burner motor H2. The burner motor is connected to the'supply line 18 by -means of conductors H3 and H4. Connected in parallel with the motor II 2 is the solenoid winding 83 by means of the conductor II5. Also whole, we will first assume that the room thermostat is satisfied, that the combustion switch is in its cold position and the burner motor is shut down. Assume now that the room temperature decreases. The flexible switch arm 98 will first engage the stationary contact I88, but as the circuit is opened at contact I84 nothing will happen at this time. A further cooling of the room thermostat will cause the rigid switch arm 99 to engage its contact 93 at which time the following circuit will be closedi from secondary 83, conductor 95, contact 94', thermostat 98, conductor I8I, contact I88, switch arms 98 and 99, contact 93, conductor 92, cold combustion switch 45, switch arm 83, conductor 9|, heater 88, conductors 81 and 86, relay winding 85 and conductor 84 back to the other side of the secondary winding 83. This circuit will energize the relay winding 85 which will pull in its swtch arms I82 and I83. Engagement of switch arms I82 and I 84 will set up a holding circuit comprising arm I83 closes its contact I88 upon energization of the relay winding 85, a circuit is set up for the burner motor as follows: supply line 11, conductor I81, contact I88, switch arm I83, conductors I89, H8 and III to the burner motor I I2 and conductors I I3 and H4 back to the other supply line 18. At the, same time the solenoid winding 83 is energized in parallel with the motor H2 by the conductor 5. The ignition means H8 will also be energized if it is connected in parallel with the burner motor II2by the conductors H1 and H8.

As explained above, the energization of the burner motor and the consequent energization of the solenoid winding 53 will cause the damper 85 in the combustion responsive device to assume a horizontal position in the tube II so that the diaphragm I5 can absorb the radiant heat from the burner the moment that combustion takes place. If combustion should fail to take place, it is understood of course that the heater 88 for the safety switch will heat the bimetallic element 9.8 to the point where it will break its contact.

with the contact 94 and therefore the relay 85 will be deenergized and the system will shut down.-

Continued heating of the diaphragm I5 will cause.

engagement of the arm 33 with its contact 42. A shunt circuit is now set up around the heater 88 which circuit comprises the conductor 9|,

switch arm 33, contact 42 and conductor II8. connected in parallel with the motor is an ignition means I I8 by means of the conductors I I1 and The heater 88 will therefore be deenergized and the safety switch will remain closed.

Due to the operation of the burner, the room will now heat up and eventually the room thermostat will cause separation of its switch arm 98 with the stationary contact I88, which will cause deenergization of the relay 85 which will in turn drop out its' relay contacts I82 and I 83.-'

As the switch arm I83 disengages its contact I88 the burner motor, ignition means and solenoid coil 83 will be deenergized. This means that the fire will go out and the return spring I4 will operate to rotate the damper 85 through an angle of so that it is placed directly across .the opening through the tube II. This will prevent any further radiant heat from striking the dia-. phragm I5 which might interfere with its cooling process. The extinguishment of the me will, as

explained above, create a partial vacuum within the combustion chamber and if the holes 16 have been provided in the annular heat insulator 13 room air will now ,be caused to flow across the diaphragm I5 through the tube H around the damper 85 and into the furnace. This passage of room air over the diaphragm will materially aid it in its cooling thereby making it more sensitive to the extinguishment of the fire. The cooling of the diaphragm will cause it to straighten out when it will break the contact between arm 33 and contact 42 and make contact between arm 33 and contact 45. The device will now be in its cold position and the above cycle may be repeated.

It should be noted also that if the system is in its running or hot position and the fire should be extinguished while the burner motor is still energized, due to a temporary stoppage in the oil line for example, the diaphragm [5 will immediately start to cool because of the sudden decrease in radiant heat from the furnace. This will cause the diaphragm to open the hot contact at 42 which will deenergize the relay 85 and hence the burner motor and cause the damper 65 to assume the position where it prevents any radiant heat from striking diaphragm l5 which wil continue to cool as explained above. The extinguishment of the fire will cause a decrease in pressure in the combustion chamber even before the burner motor is shut down so that the room air blowing against the diaphragm will help cool it immediately the fire is extinguished.

It will therefore be seen that in this invention I have provided a device which will aid in making a radiant heat responsive thermostat more sensitive to the extinguishment of the fire in that it will not only prevent the further absorption of heat from the furnace but will also cause a more rapid dissipation of heat from the heat responsive device.

Certain changes and modifications of this invention may occur to those who are skilled in the art and it is therefore to be understood that I am to be limited not by the embodiment disclosed herein but rather by the scope of the appended claims.

I claim as my invention:

1. In a burner control system in combination, a' furnace, a fuel burner for producing a fire in said furnace, a heat responsive device located in the wall of said furnace in a position to absorb radiant heat from the fire produced by said fuel burner, control means for energizing and deenergizing said fuel burner, said control means including means operated by said heat responsive device, and means permitting radiant heat from said fire to pass to said heat responsive device when saidburner is energized and preventing radiant heat from passing to said heat responsive device when saidburner is deenergized.

2. In a burner control system in combination, a furnace, a fuel burner for producing a fire in said furnace, a heat'responsive device comprising an elongated tube, a thermostat located at one end of said tube, the other end of said tube being open, means for mounting said device in the wall of said furnace so that the open end of the tube confronts the fire thereby permitting radiant heat passing directly to the thermostat, control means for energizing and deenergizing said fuel burner, said control means including.

means operated by said heat responsive device, and means for deenergizing the fuel burner and preventing radiant heat from passing from the furnace to said thermostat when the fire is extinguished.

3. In a burner control system in combination, a furnace, a fuel burner for producing a fire in said furnace, a heat responsive device comprising an elongated tube, a thermostat located at one end of said tube, the other end of said tube being open, means for mounting said device in the wall of said furnace so that the open end of the tube confronts the fire thereby permitting radiant heat passing directly to the thermostat, control means for energizing and deenergizing said fuel burner, said control means including means operated by said heat responsive device, a damper mounted within said tube on an axis extending transversely of said tube, a solenoid connected to said damper for rotating said damper to a position where it does not interfere substantially with the radiant heat passing from the furnace to the thermostat, a. spring for rotating the damper to a position directly across the tube when said solenoid is deenergized, and means for energizing said solenoid simultaneously with said fuel burner.

4. In a burner control system in combination, a furnace, a fuel burner for producing a fire in said furnace, a heat responsive device comprising an elongated tube, a heat sensitive diaphragm clamped at its periphery closing oneend of said tube, the other end of said tube being open, means for mounting said device in the wall of said furnace so that the open end of the tube confronts the fire thereby permitting radiant heat passing directly to said diaphragm from said fire, switch means operated by said diaphragm, control means including said switch means for energizing said fuel burner, so that when the burner is energized the diaphragm will heat up and operate the switch'means in one direction, and when the burner is deenergized the diaphragm will cool of! and operate the switch means in the opposite direction, a damper mounted within saidtube on an axis extending transversely of said tube, a solenoid connected to said damper for rotating to a position where it does not interfere substantially with the radiant heat passing from the furnace to the thermostat, a spring for rotating the damper to a position directly across the tube when said solenoid is deenergized, and means for energizing said solenoid simultaneously with said fuel burner, and holes cut in the tube near the diaphragm so that upon deenergization of the burner-the natural draft through the furnace will draw room air over the diaphragm and into the furnace, said damper being a loose fit within said tube to permit such passage of air.

5. A heat responsive device comprising in combination, a furnace, a fuel burner for producing a flame within said furnace, an elongated tube, a heat sensitive diaphragm clamped at its periphery closing one end of said tube, control means for said fuel burner operated by said diaphragm, the other end of said tube being open and being adapted to be positioned so that radiant heat from said flame can pass through said tube and onto said diaphragm, a damper pivoted within said tube, an electric motor for moving said damper to one position so that it will have substantially no effect on the radiant heat passing through said tube, and means for moving said damper to a position directly acros said tube when said motor and fuel burner are deenergized.

6. A heat responsive device comprising in combination, a furnace, a fuel burner for producing for said fuel burner operated by said diaphragm,

the other end of said tube being open and being adapted to be positioned so that radiant heat from said flame can pass through said tube and onto said diaphragm, a damper pivoted within said tube, an electric motor for moving said damper to one position so that it will have sub 7 stantiaily no eifect on the radiant heat passing through said tube, means for moving said damper to a position directly across said tube when said motor and fuel burner are deenergized, and holes cut through the tube near the diaphragm so that when said damper is located across said tube air from outside said tube may pass over said diaphragm and help cool it.

"I. A heat responsive device comprising in combination, an elongated tube having an open end and a closed end, aheat sensitive device located at the closed end of said tube, a furnace, means for producing a fire in said furnace, control means for said fire producing means including said heat sensitive device, means for mounting said devicein a wall of said furnace so that the open end of the tube confronts the fire, the heat sensitive device being located outside of the furnace and responding to the radiant heat passing from the furnace through the tube, holes cut in the tube for directing room air against the heat sensitive device when the furnace pressure is below atmospheric due to fire extinguishment, and means operated by the heat sensitive device upon a response due to the extinguishment of the fire for preventing radiant heat from .passing to the heat sensitive device from the furnace. Y

8. A burner control system comprising in combination, a combustion chamber, a burner for producing a fire in said chamber, a combustion responsive device positioned in the path of radiant heat from said combustion chamber, control means for said burner including said combustion responsive device, and means normally preventing radiant heat from said combustion chamber striking'said combustion responsive device, but permitting such action whenever said burner is energized.

' ROBERT A. BEVERIDGE. 28) 

